There is an increasing trend to include radar systems in commercially available automotive products such as automobiles, trucks, buses, and the like in order to provide a driver with enhanced awareness of objects around his or her vehicle. As the vehicle approaches objects (e.g. other cars, pedestrians, and obstacles) or as objects approach the vehicle, a driver cannot always detect the object and perform intervention actions needed to avoid a collision with the object. For example, a driver of a vehicle may not be able to detect an object in the so-called “blind spot” of the vehicle. This blind spot region varies depending on the type of vehicle, the size and seated position of the driver, the type and setting of the outside minors, and so forth. An automotive radar system mounted on a vehicle can detect the presence of objects including other vehicles in proximity to the vehicle and provide the driver with timely information so that the driver can perform possible intervention actions. In order to effectively detect the presence of objects in the regions of limited visibility, such as in the blind spot, automotive radar systems typically include multiple beam antennas to provide wide coverage area.
FIG. 1 shows a diagram of a vehicle 20 with a prior art automotive radar system 22 disposed on a side thereof. Automotive radar system 22 may be provided as a side object detection system (SOD), sometimes referred to as a blind spot detection system. A typical prior art automotive radar system, such as radar system 22, includes a planar array antenna capable of generating multiple antenna beam patterns or radiation patterns. In this illustration, four antenna beam patterns (or more simply “beams”) 24A, 24B, 24C, and 24D are shown. For automotive radar applications, beam patterns 24A, 24B, 24C, and 24D are arranged such that their vertical patterns (or elevation) are narrow and parallel to the surface of road 26, and their horizontal (or azimuth) patterns generally cover the nominally quarter plane parallel to the surface of road 26 and are limited by the edge of vehicle 20 and the location of radar system 22 on vehicle 20.
Radar system 22 is capable of detecting with high probability objects, such as other vehicles, moving along a path 28 which is parallel to the path of vehicle 20 in which radar system 22 is disposed. The objects may be, for example, other vehicles approaching and passing vehicle 20. In this exemplary scenario, two objects are present in a lane 30 adjacent to a lane 32 in which vehicle 20 is traveling. One object 34, labeled “A,” may be adjacent vehicle 20, and another object 36, labeled “B,” may be approaching and overtaking vehicle 20. In order to effectively detect objects 34 and 36, multiple antenna beam patterns (e.g., beams 24A, 24B, 24C, and 24D) from a radar antenna are called for to provide sufficient angular coverage and antenna gain. For example, in response to a radar signal transmitted from radar system 22, a receive signal 38 reflected from object 34 and detectable within beam pattern 24D can identify the probable presence of object 34 in lane 30. Similarly, in response to a radar signal transmitted from radar system 22, a receive signal 40 reflected from object 36 and detectable within beam pattern 24A can identify the probable presence of object 36 in lane 30.
Additional multipath signal components referred to as indirect receive signals 41 may also be received at radar system 22. Indirect receive signals 41 may be reflections of the radar signal from an object (e.g., object 34 and/or object 36) onto a reflective panel of, for example, vehicle 20. These reflections are subsequently reflected off the reflective panel and are received at a receiving antenna of radar system 22. Indirect receive signals are considered interference, or nuisance signals, and are typically filtered or otherwise attenuated by most radar configurations, such as the multiple beam antenna configuration of radar system 22.
Relatively strict requirements are imposed on the physical size, the operational performance, and the cost of automotive radar systems. Unfortunately, multiple beam antenna systems are complex and thus result in relatively high cost systems.